Method of operating smart card and method of operating smart card system including the same

ABSTRACT

A smart card may include data storage and transmission circuitry, a plurality of voltage controllers to supply operational power to card circuitry, a plurality of oscillators to supply an internal clock for the card, and power management circuitry. The power management circuitry may be configured to shut down the oscillators and at least one, but not all, voltage controllers during a period after a data transmission is completed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC §119 to Korean PatentApplications No. 10-2014-0121610, filed on Sep. 15, 2014, in the KoreanIntellectual Property Office (KIPO), the contents of which are hereinincorporated by reference in their entirety.

BACKGROUND

1. Technical Field

Exemplary embodiments relate generally to a smart card and moreparticularly to a method of operating a smart card and a method ofoperating a smart card system.

2. Description of the Related Art

A smart card may perform functions using, for example, a micro-processorand an operating system included in the smart card. Researches is inprogress to decrease power consumption of a smart card.

SUMMARY

Some exemplary embodiments provide a method of operating a smart cardcapable of decreasing power consumption by controlling voltages that areprovided to sub-units, based on a control signal and level controlsignals during a clock stop time interval.

In a method of operating a smart card according to exemplaryembodiments, a power management unit deactivates a plurality ofsub-units based on a plurality of enable signals during a first idletime interval. A first stop signal is a second logic level and a secondstop signal is a first logic level based on a external clock signalduring the first idle time interval after data transmission iscompleted. The power management unit and a frequency detector controlvoltages based on a control signal and level control signals during aclock stop time interval. The voltages are provided to the sub-units.The control signal is generated from the frequency detector. The levelcontrol signals are generated from the power management unit based onthe control signal. The first stop signal is the second logic level andthe second stop signal is the second logic level based on the externalclock signal during the clock stop time interval after the first idletime interval. The power management unit activates the plurality ofsub-units based on the plurality of enable signals during a second idletime interval. The first stop signal is the second logic level and thesecond stop signal is the first logic level based on the external clocksignal during the second idle time interval after the clock stop timeinterval.

The plurality of sub-units may include an internal voltage control unitand an oscillator unit. The internal voltage control unit may include aplurality of active voltage controllers and a plurality of stop voltagecontrollers. The oscillator unit may include a plurality of oscillators.The plurality of active voltage controllers, the plurality of stopvoltage controllers and the plurality of oscillators may be activatedand deactivated based on the plurality of enable signals.

The external clock signal may be activated during the first idle timeinterval. During the first idle time interval, the plurality ofoscillators may be sequentially turned-off based on oscillator enablesignals of the plurality of enable signals.

During the first idle time interval, the plurality of stop voltagecontrollers may be turned-on based on stop voltage controller enablesignals of the plurality of enable signals. The plurality of activevoltage controllers may be sequentially turned-off based on activevoltage controller enable signals of the plurality of enable signals.

The external clock signal may be deactivated during the clock stop timeinterval. During the clock stop time interval, the frequency detectormay stop detecting whether a frequency of the external clock signal isin a predetermined range and may detect whether the external clocksignal is activated or not. The frequency detector and the powermanagement unit may control the voltages based on stop voltage controlsignals of the level control signals and the control signal during theclock stop time interval. The voltages may be provided to the stopvoltage controllers. The level control signals may be generated from thepower management unit based on the control signal.

The stop voltage controllers may include a first stop voltage controllerand a second stop voltage controller. A level of a first stop voltagethat is provided from the first stop voltage controller may be differentfrom a level of a second stop voltage that is provided from the secondstop voltage controller.

The first stop voltage that is provided from the first stop voltagecontroller may be provided to a logic circuit unit included in the smartcard. The second stop voltage that is provided from the second stopvoltage controller may be provided to SRAM included in the smart card.

During the clock stop time interval, the plurality of oscillators may beturned-off. During the clock stop time interval, the stop voltagecontrollers may be turned-on and the active voltage controllers may beturned-off.

The external clock signal may be activated during the second idle timeinterval. During the second idle time interval, the plurality ofoscillators may be sequentially turned-on based on oscillator enablesignals of the plurality of enable signals.

During the second idle time interval, the stop voltage controllers maybe turned-on based on stop voltage controller enable signals. During thesecond idle time interval, the plurality of active voltage controllersmay be sequentially turned-on based on active voltage controller enablesignals of the plurality of enable signals.

The plurality of sub-units may further include a detector unit. Thedetector unit may include a plurality of detectors that detect internalenvironment of the smart card. The plurality of detectors may beactivated and deactivated based on the plurality of enable signals.

During the first idle time interval, the plurality of detectors may besequentially turned-off based on detector enable signals of theplurality of enable signals. During the clock stop time interval, theplurality of detectors may be turned-off. During the second idle timeinterval, the plurality of detectors may be sequentially turned-on basedon the detector enable signals.

The plurality of sub-units may further include a reset unit. The resetunit may reset the smart card in the event internal voltage of the smartcard is less than a predetermined voltage. During the clock stop timeinterval, the reset unit may be turned-off based on a reset enablesignal of the plurality of enable signals.

The plurality of sub-units may further include a pad unit that receivesexternal signals. During the clock stop time interval, the pad unit maybe turned-on and turned-off based on a pad enable signal of theplurality of enable signals.

In a method of operating a smart card according to exemplaryembodiments, a power management unit deactivates a plurality ofsub-units based on a plurality of enable signals during a first stoptime interval. A first stop signal is a second logic level and a secondstop signal is a first logic level based on the first stop signal duringthe first stop time interval after data transmission is completed. Thepower management unit and a frequency detector control voltages based ona control signal and level control signals during a second stop timeinterval after the first stop time interval. The voltages are providedto the sub-units. The control signal is generated from the frequencydetector. The level control signals are generated from the powermanagement unit based on the control signal. The power management unitactivates the plurality of sub-units based on the plurality of enablesignals during a third stop time interval. The third stop time intervalis before the first stop signal transitions from the second logic levelto the first logic level after the second stop time interval.

A method of operating a smart card according to exemplary embodimentsmay decrease power consumption by controlling voltages that are providedto sub-units, based on a control signal and level control signals duringa clock stop time interval.

In exemplary embodiments in accordance with principles of inventiveconcepts a smart card includes data storage and transmission circuitry;a plurality of voltage controllers to supply operational power to cardcircuitry; a plurality of oscillators to supply an internal clock forthe card; and power management circuitry to shut down the oscillatorsand at least one, but not all, voltage controllers during a period aftera data transmission is completed.

In exemplary embodiments in accordance with principles of inventiveconcepts a smart card includes power management circuitry configured toreduce the voltage output of a voltage controller that has not been shutdown when an external clock is deactivated.

In exemplary embodiments in accordance with principles of inventiveconcepts a smart card includes power management circuitry configured toturn on the oscillators and voltage controllers that had been shut downand to return the output voltage of a voltage controller whose outputvoltage had been reduced when the external clock is activated.

In exemplary embodiments in accordance with principles of inventiveconcepts a smart card includes power management circuitry configured toshut down the oscillators in sequence.

In exemplary embodiments in accordance with principles of inventiveconcepts a smart card includes power management circuitry shuts down aplurality of voltage controllers in sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative, non-limiting exemplary embodiments will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings.

FIG. 1 is a flow chart illustrating a method of operating a smart cardaccording to exemplary embodiments.

FIG. 2 is a timing diagram for describing the method of operating thesmart card of FIG. 1.

FIG. 3 is a block diagram illustrating a smart card according toexemplary embodiments.

FIG. 4 is a block diagram illustrating an example of an internal voltagecontrol unit included in the smart card of FIG. 3.

FIG. 5 is a block diagram illustrating an example of an oscillator unitincluded in the smart card of FIG. 3.

FIG. 6 is a timing diagram for describing an operation of an oscillatorunit included in the smart card of FIG. 3 during a first idle timeinterval.

FIG. 7 is a timing diagram for describing an operation of an internalvoltage control unit included in the smart card of FIG. 3 during a firstidle time interval.

FIG. 8 is a timing diagram for describing states of an oscillator unitand an internal voltage control unit included in the smart card of FIG.3 during a first idle time interval.

FIG. 9 is a timing diagram for describing an operation of an internalvoltage control unit included in the smart card of FIG. 3 during a clockstop time interval.

FIG. 10 is a diagram for describing operations of stop voltagecontrollers included in the internal voltage control unit of FIG. 4.

FIG. 11 is a timing diagram for describing an operation of an oscillatorunit included in the smart card of FIG. 3 during a clock stop timeinterval.

FIG. 12 is a timing diagram for describing states of an oscillator unitand an internal voltage control unit included in the smart card of FIG.3 during a clock stop time interval.

FIG. 13 is a timing diagram for describing an operation of an oscillatorunit included in the smart card of FIG. 3 during a second idle timeinterval.

FIG. 14 is a timing diagram for describing an operation of an internalvoltage control unit included in the smart card of FIG. 3 during asecond idle time interval.

FIG. 15 is a timing diagram for describing states of an oscillator unitand an internal voltage control unit included in the smart card of FIG.3 during a second idle time interval.

FIG. 16 is a diagram for describing operations of an oscillator unit andan internal voltage control unit included in the smart card of FIG. 3during a first idle time interval, a clock stop time interval and asecond idle time interval.

FIG. 17 is a diagram illustrating a current specification according toETSI TS 102 221 that is a specification of a smart card.

FIG. 18 is a block diagram illustrating a smart card according to anexemplary embodiment.

FIG. 19 is a block diagram illustrating an example of a detector unitincluded in the smart card of FIG. 18.

FIG. 20 is a diagram for describing operations of a detector unitincluded in the smart card of FIG. 18 during a first idle time interval,a clock stop time interval and a second idle time interval.

FIG. 21 is a block diagram illustrating a smart card according toexemplary embodiments.

FIG. 22 is a diagram for describing an operation of a reset unitincluded in the smart card of FIG. 21.

FIG. 23 is a flow chart illustrating a method of operating a smart cardsystem according to exemplary embodiments.

FIG. 24 is a block diagram illustrating a smart card system according toexemplary embodiments.

FIG. 25 is a flow chart illustrating a method of operating a smart cardaccording to exemplary embodiments.

FIG. 26 is a timing diagram for describing the method of operating thesmart card of FIG. 25.

FIG. 27 is a block diagram illustrating a mobile system according to anexemplary embodiment.

DETAILED DESCRIPTION

Various exemplary embodiments will be described more fully hereinafterwith reference to the accompanying drawings, in which some exemplaryembodiments are shown. Inventive concepts may, however, be embodied inmany different forms and should not be construed as limited to theexemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of inventive concepts to thoseskilled in the art. In the drawings, the sizes and relative sizes oflayers and regions may be exaggerated for clarity. Like numerals referto like elements throughout.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These tell is are used to distinguish oneelement from another. Thus, a first element discussed below could betermed a second element without departing from the teachings of thepresent inventive concept. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularexemplary embodiments only and is not intended to be limiting ofinventive concepts. As used herein, the singular forms “a,” “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

It should also be noted that in some alternative implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved.

Unless otherwise defined, all terms (including technical and scientificteens) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which inventive concepts belong. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andshall not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

A smart card in accordance with principles of inventive concepts mayinclude a plurality of voltage controllers and oscillators which itoperates to conserve power during intervals between data transmissionsthat occur between the smart card and a card reader. At least onevoltage controller may be of a first, “active,” operational type and atleast one may be of a second, “stop,” operational type. Activeoperational types operate at nominal voltages during card operationssuch as data transmission, but are turned off during idle periods(thereby cutting off power to circuits to which they supply power); stopoperational types continue to operate during idle periods, but mayoperate at reduced voltage levels during some idle periods (therebyreducing power supplied to circuits during the low-voltage periods).

Relatively inactive smart card periods between data transmission may bebroken down into: a first idle period (also referred to herein as idletime interval 1), which may occur during the time after a datatransmission has been completed and the time that an external clockstops oscillating; a second idle period (also referred to herein as aclock stop interval) may occur during the time from the stopping of theexternal clock until the external clock begins to oscillate again; and athird idle period (also referred to herein as idle time interval 2) mayoccur from the time the external clock resumes oscillation until anotherdata transmission is initiated.

In exemplary embodiments, during the first idle period the oscillatorsare shut down (sequentially, if more than one) and the one or moreactive voltage controllers are shut down (sequentially, if more thanone). During the second idle period the oscillators and active voltagecontrollers remain “off” and the stop voltage controllers are operatedat a reduced voltage level. During the third idle period the oscillatorsare restarted, (in a reverse sequence, for example), active voltagecontrollers are restarted (in a reverse sequence, for example), and stopvoltage controllers return to nominal voltage level operation from theirreduced voltage level operation.

FIG. 1 is a flow chart illustrating a method of operating a smart cardaccording to exemplary embodiments, FIG. 2 is a timing diagram fordescribing a method of operating the smart card of FIG. 1 and FIG. 3 isa block diagram illustrating a smart card according to exemplaryembodiments.

Referring to FIGS. 1 to 3, a smart card 10 may include a CPU 100, apower management unit 200, a plurality of sub-units 300 and a frequencydetector 400. The smart card 10 may receive a power supply voltage VDD,an external clock signal ECLK and an input-output signal SIO. When datatransmission is completed between the smart card 10 and a card reader,the CPU 100 may provide a power stop command C_PO to the powermanagement unit 200. The power management unit 200 may activate ordeactivate the sub-units 300 based on, that is, using, the enablesignals EN_VC, EN_OS. Sub-units 300 may include an internal voltagecontrol unit 310 and an oscillator unit 330. The internal voltagecontrol unit 310 may provide an internal voltage based on, that is, inresponse to, a voltage controller enable signals EN_VC of the enablesignals EN_VC, EN_OS that are provided from the power management unit200. The oscillator unit 330 may provide an internal clock signal OSCbased on, that is, in response to, an oscillator enable signal EN_OS ofthe enable signals EN_VC, EN_OS that are provided from the powermanagement unit 200.

In the event the power management unit 200 deactivates the sub-units 300based on the enable signals EN_VC, EN_OS, the power supply voltage thatis provided to the sub-units 300 may be blocked. For example, in theevent the power management unit 200 disables the voltage controllerenable signal EN_VC of the enable signals EN_VC, EN_OS, the power supplyvoltage to the internal voltage control unit 310 may be blocked, orturned off, and, in turn, operation of the internal voltage control unit310 may be stopped. In the event the power management unit 200 disablesthe oscillator enable signal EN_OS of the enable signals EN_VC, EN_OS,the power supply voltage to the oscillator unit 330 may be blocked, orturned off, and, in turn, operation of the oscillator unit 330 may bestopped.

In the event the power management unit 200 activates the sub-units 300based on the state of enable signals EN_VC, EN_OS, the power supplyvoltage may be provided to the sub-units 300. For example, in the eventthe power management unit 200 enables the voltage controller enablesignal of the enable signals EN_VC, EN_OS, the power supply voltage maybe provided to the internal voltage control unit 310 and, as a result,the internal voltage control unit 310 may normally operate. In the eventthe power management unit 200 enables the oscillator enable signal EN_OSof the enable signals EN_VC, EN_OS, the power supply voltage may beprovided to the oscillator unit 330 and, as a result, the oscillatorunit 330 may normally operate.

The frequency detector 400 may detect whether the frequency of theexternal clock signal ECLK is within a predetermined range or not.During the clock stop time interval CSTI, the frequency detector 400 maystop detecting whether the frequency of the external clock signal ECLKis in the predetermined range and may detect only whether the externalclock signal ECLK is activated or not. During the clock stop timeinterval CSTI, the power management unit 200 and a frequency detector400 control voltages provided to sub-units 300 based on a control signalCS_SVC and level control signals L_CS_SVC. The control signal CS_SVC isgenerated from the frequency detector 400 by detecting the externalclock signal ECLK. The level control signals L_CS_SVC are generated fromthe power management unit 200 based on the control signal CS_SVC. In theevent the external clock signal ECLK is disabled, the frequency detector400 may provide the control signal CS_SVC to the internal voltagecontrol unit 310 and the power management unit 200 by detecting thedeactivation of the external clock signal ECLK. The power managementunit 200 may generate the level control signals L_CS_SVC based on thecontrol signal CS_SVC. The power management unit 200 may control thevoltages that are provided to the sub-units 300, based on the levelcontrol signals L_CS_SVC. A time interval when the external clock signalECLK is deactivated may be the clock stop time interval CSTI. The levelof the voltages that are provided to the sub-units 300 may be controlledbased on the control signal CS_SVC and the level control signalsL_CS_SVC. In the event the level of the voltages that are provided tothe sub-units 300 is controlled, the level of the output voltages thatare outputted from the sub-units 300 may be controlled.

In a method of operating a smart card 10 according to exemplaryembodiments, a power management unit 200 deactivates a plurality ofsub-units 300 based on a plurality of enable signals EN_VC, EN_OS duringa first idle time interval ITI1 (S100). A first stop signal SS1 is asecond logic level and a second stop signal SS2 is a first logic levelbased on, or in response to, an external clock signal ECLK during thefirst idle time interval ITI1 after data transmission is completed. Thesecond stop signal SS2 may be generated from a frequency detector 400based on an external clock signal ECLK. For example, the first logiclevel may be a logic low level and the second logic level may be a logichigh level. When data transmission is completed between the smart card10 and a card reader, the CPU 100 may provide the power stop commandC_PO to the power management unit 200 and, as a result, the first stopsignal SS1 may transition from the first logic level to the second logiclevel. Then, during the clock stop time interval CSTI, the frequencydetector 400 may stop detecting whether the frequency of the externalclock signal ECLK is within the predetermined range and may detect onlywhether the external clock signal ECLK is activated or not. Thefrequency detector 400 may detect the external clock signal ECLK. In theevent the external clock signal ECLK is deactivated, the frequencydetector 400 may detect the deactivation of the external clock signalECLK. In the event the frequency detector 400 detects the deactivationof the external clock signal ECLK, the second stop signal SS2 maytransition from the first logic level to the second logic level. Thefirst idle time interval ITI1 may be a time interval when the first stopsignal SS1 is the second logic level and the second stop signal SS2 isthe first logic level after the data transmission is completed.

The power management unit 200 and a frequency detector 400 controlvoltages provided to sub units 300 based on a control signal CS_SVC andlevel control signals L_CS_SVC during a clock stop time interval CSTI(S110). The control signal CS_SVC is generated from the frequencydetector 400. The level control signals L_CS_SVC are generated from thepower management unit 200 based on the control signal CS_SVC. The firststop signal SS1 is the second logic level and the second stop signal SS2is the second logic level based on the external clock signal ECLK duringthe clock stop time interval CSTI after the first idle time intervalITI1. For example, during the clock stop time interval CSTI, thefrequency detector 400 may stop detecting whether the frequency of theexternal clock signal ECLK is within the predetermined range and maydetect only whether the external clock signal ECLK is activated or not.The frequency detector 400 may detect the external clock signal ECLK. Inthe event the external clock signal ECLK is deactivated, the frequencydetector 400 may detect the deactivation of the external clock signalECLK. In the event the frequency detector 400 detects the deactivationof the external clock signal ECLK, the second stop signal SS2 maytransition from the first logic level to the second logic level. Whilethe external clock signal ECLK is deactivated, the second stop signalSS2 may be the second logic level.

During the clock stop time interval CSTI, the power supply voltage maybe required in a part of the sub-units 300. In this case, during theclock stop time interval CSTI, a voltage level of the power supplyvoltage that is provided to the part of the sub-units 300 during theclock stop time interval CSTI may be less than the voltage level of thepower supply voltage that is provided to the sub-units 300 during anactive time interval when the data is transferred between the smart card10 and the card reader. During the clock stop time interval CSTI, thevoltage level of the power supply voltage that is provided to the partof the sub-units 300 may be decreased in order to reduce currentconsumption in sub-units 300.

The power management unit 200 activates the plurality of sub-units 300based on the plurality of enable signals EN_VC, EN_OS during a secondidle time interval ITI2 (S120). The first stop signal SS1 is the secondlogic level and the second stop signal SS2 is the first logic levelbased on the external clock signal ECLK during the second idle timeinterval ITI2 after the clock stop time interval CSTI. For example, thefirst stop signal SS1 may be the second logic level until theinput-output signal SIO transitions to the logic low level after theclock stop time interval CSTI. In the event the external clock signalECLK is activated after the clock stop time interval CSTI, the secondstop signal SS2 may transition from the second logic level to the firstlogic level. The second idle time interval ITI2 may be a time intervalwhen the first stop signal SS1 is the second logic level and the secondstop signal SS2 is the first logic level after the clock stop timeinterval CSTI.

A method of operating a smart card 10 according to exemplary embodimentsmay decrease the power consumption by controlling the voltages that areprovided to the sub-units 300 based on the control signal CS_SVC and thelevel control signals L_CS_SVC during the clock stop time interval CSTI.

FIG. 4 is a block diagram illustrating an example of an internal voltagecontrol unit included in the smart card of FIG. 3 and FIG. 5 is a blockdiagram illustrating an example of an oscillator unit included in thesmart card of FIG. 3.

Referring to FIGS. 4 and 5, the plurality of sub-units 300 may includean internal voltage control unit 310 and an oscillator unit 330. Theinternal voltage control unit 310 may include a plurality of activevoltage controllers 311 to 313 and a plurality of stop voltagecontrollers 314 and 315. The oscillator unit 330 may include a pluralityof oscillators 331 to 333. The plurality of active voltage controllers311 to 313, the plurality of stop voltage controllers 314 and 315 andthe plurality of oscillators 331 to 333 may be activated and deactivatedusing the plurality of enable signals EN_VC, EN_OS.

The internal voltage control unit 310 may provide internal voltages usedin the smart card 10 based on the power supply voltage VDD. The activevoltage controllers 311 to 313 included in the internal voltage controlunit 310 may provide the internal voltages ACTIVE IVC1 to ACTIVE IVC3used in the smart card 10 during the active time interval. The stopvoltage controllers 314 and 315 included in the internal voltage controlunit 310 may provide the internal voltages STOP IVC1 to STOP IVC2 usedin the smart card 10 during the stop mode time interval.

For example, during an active time interval, the first to third activevoltage controller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 may beenabled, in which case, the first to third active voltage controllers311 to 313 may be normally operated. In the event the first to thirdactive voltage controllers 311 to 313 are normally operated, the firstto third active voltage controllers 311 to 313 may provide a firstvoltage. For example the first voltage may be 1.1V. For example, duringactive time interval, the first to second stop voltage controller enablesignals EN_SVC1 and EN_SVC2 may be enabled, in which case, the first tosecond stop voltage controllers 314 and 315 may be normally operated. Inthe event the first to second stop voltage controllers 314 and 315 arenormally operated, the first to second stop voltage controllers 314 and315 may provide a first voltage. For example the first voltage may be1.1V.

For example, the stop mode time interval may include the first idle timeinterval ITI1, the clock stop time interval CSTI and the second idletime interval ITI2. During the clock stop time interval CSTI of the stopmode time interval, the first to third active voltage controller enablesignals may be disabled, in which case, the first to third activevoltage controllers 311 to 313 may not be operated. In the event thefirst to third active voltage controllers 311 to 313 are not operated,the first to third active voltage controllers 311 to 313 may provide aground voltage. For example, during the clock stop time interval CSTI,the first to second stop voltage controller enable signal may beenabled, in which case, the first to second stop voltage controllers 314and 315 may be normally operated. In the event the first to second stopvoltage controllers 314 and 315 are normally operated, the first tosecond stop voltage controllers 314 and 315 may provide the firstvoltage, which may be 1.1V.

The first to third oscillators 331 to 333 may be turned-on or turned-offbased on the first to third oscillator enable signals EN_OS1, EN_OS2 andEN_OS3. In the event the first to third oscillator enable signalsEN_OS1, EN_OS2 and EN_OS3 are enabled, the first to third oscillators331 to 333 may provide a first to third clock signals.

FIG. 6 is a timing diagram for describing operation of an oscillatorunit included in the smart card of FIG. 3 during a first idle timeinterval.

Referring to FIG. 6, the first idle time interval ITI1 may be a timeinterval when the first stop signal SS1 is the second logic level andthe second stop signal SS2 is the first logic level after the datatransmission is completed.

In an exemplary embodiment, the external clock signal ECLK may beactivated during the first idle time interval ITI1. For example, thefrequency detector 400 may detect the external clock signal ECLK. In theevent the external clock signal ECLK is deactivated, the frequencydetector 400 may control the second stop signal SS2 so that the secondstop signal SS2 transitions from the first logic level to the secondlogic level. During the first idle time interval ITI1, the externalclock signal ECLK may be activated. During the clock stop time intervalCSTI, the external clock signal ECLK may be deactivated. During thesecond idle time interval ITI2, the external clock signal ECLK may beactivated.

In an exemplary embodiment, during the first idle time interval ITI1,the plurality of oscillators 331 to 333 may be sequentially turned-offbased on oscillator enable signals EN_OS1, EN_OS2 and EN_OS3 of theplurality of enable signals EN_VC, EN_OS. For example, the oscillators331 to 333 may include a first oscillator 331, a second oscillator 332and a third oscillator 333. The oscillator enable signals EN_OS1, EN_OS2and EN_OS3 of the enable signals EN_VC, EN_OS may include a first tothird oscillator enable signals EN_OS1, EN_OS2 and EN_OS3. During thefirst idle time interval ITI1, the first to third oscillator enablesignals EN_OS1, EN_OS2 and EN_OS3 may be sequentially disabled. Forexample, during the first idle time interval ITI1, the second oscillatorenable signal EN_OS2 may be disabled after the first oscillator enablesignal EN_OS1 is disabled and the third oscillator enable signal EN_OS3may be disabled after the second oscillator enable signal EN_OS2 isdisabled. As a result, the second oscillator 332 may be turned-off afterthe first oscillator 331 is turned-off and the third oscillator 333 maybe turned-off after the second oscillator 332 is turned-off.

FIG. 7 is a timing diagram for describing operation of an internalvoltage control unit included in the smart card of FIG. 3 during a firstidle time interval.

Referring to FIGS. 4 and 7, the internal voltage control unit 310 mayinclude a plurality of active voltage controllers 311 to 313 and aplurality of stop voltage controllers 314 and 315. The active voltagecontrollers 311 to 313 may include a first active voltage controller311, a second active voltage controller 312 and a third active voltagecontroller 313. The stop voltage controllers 314 and 315 may include afirst stop voltage controller 314 and a second stop voltage controller315. For example, the first to third active voltage controllers 311 to313 may provide first to third active voltages based on, in response to,the first to third active voltage controller enable signals EN_AVC1,EN_AVC2 and EN_AVC3. The first to second stop voltage controllers 314and 315 may provide a first to second stop voltages based on, inresponse to, the first to second stop voltage controller enable signalsEN_SVC1 and EN_SVC2.

In an exemplary embodiment, during the first idle time interval ITI1,the plurality of stop voltage controllers 314 and 315 may be turned-onbased on stop voltage controller enable signals EN_SVC1 and EN_SVC2 ofthe plurality of enable signals EN_VC, EN_OS. For example, during thefirst idle time interval ITI1, the first to second stop voltagecontroller enable signals EN_SVC1 and EN_SVC2 may be enabled and, as aresult, the first to second stop voltage controllers 314 and 315 may beturned-on.

In an exemplary embodiment, the plurality of active voltage controllers311 to 313 may be sequentially turned-off based on active voltagecontroller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 of the pluralityof enable signals EN_VC, EN_OS. For example, the first to third activevoltage controller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 may besequentially disabled during the first idle time interval ITI1, with thesecond active voltage controller enable signal EN_AVC2 may be disabledafter the first active voltage controller enable signal EN_AVC1 isdisabled and the third active voltage controller enable signal EN_AVC3may be disabled after the second active voltage controller enable signalEN_AVC2 is disabled. As a result, the second active voltage controller312 may be turned-off after the first active voltage controller 311 isturned-off and the third active voltage controller 313 may be turned-offafter the second active voltage controller 312 is turned-off.

FIG. 8 is a timing diagram for describing states of an oscillator unitand an internal voltage control unit included in the smart card of FIG.3 during a first idle time interval.

Referring to FIGS. 4, 5 and 8, the plurality of sub-units 300 mayinclude an internal voltage control unit 310 and an oscillator unit 330.The internal voltage control unit 310 may include a plurality of activevoltage controllers 311 to 313 and a plurality of stop voltagecontrollers 314 and 315. The oscillator unit 330 may include a pluralityof oscillators 331 to 333. the first idle time interval ITI1 may be atime interval when the first stop signal SS1 is the second logic leveland the second stop signal SS2 is the first logic level after the datatransmission is completed.

During the first idle time interval ITI1, the active voltage controllers311 to 313 included in the internal voltage control unit 310, theoscillators 331 to 333 included in the oscillator unit 330 may besequentially turned-off and the stop voltage controllers 314 and 315included in the internal voltage control unit 310 may be turned-on.

FIG. 9 is a timing diagram for describing operation of an internalvoltage control unit included in the smart card of FIG. 3 during a clockstop time interval.

Referring to FIGS. 3, 4 and 9, the clock stop time interval CSTI may bea time interval when the first stop signal SS1 and the second stopsignal SS2 are the second logic level.

In an exemplary embodiment, the external clock signal ECLK may bedeactivated during the clock stop time interval CSTI. For example,during the clock stop time interval CSTI, the frequency detector 400 maystop detecting whether the frequency of the external clock signal ECLKis within the predetermined range and may detect only whether theexternal clock signal ECLK is activated or not. The frequency detector400 may detect the external clock signal ECLK. In the event the externalclock signal ECLK is deactivated, the frequency detector 400 may controlthe second stop signal SS2 so that the second stop signal SS2transitions from the first logic level to the second logic level. Duringthe first idle time interval ITI1, the external clock signal ECLK may beactivated. During the clock stop time interval CSTI, the external clocksignal ECLK may be deactivated. During the second idle time intervalITI2, the external clock signal ECLK may be activated.

In an exemplary embodiment, the frequency detector 400 and the powermanagement unit 200 may control voltages which may be provided to thestop voltage controllers 314 and 315 based on stop voltage controlsignals of the level control signals L_CS_SVC and the control signalCS_SVC during the clock stop time interval CSTI. The level controlsignals L_CS_SVC may be generated from the power management unit 200based on the control signal CS_SVC. For example, the stop voltagecontrol signal may include a first stop voltage control signal L_CS_SVC1and a second stop voltage control signal L_CS_SVC2. The stop voltagecontrollers 314 and 315 may include a first stop voltage controller 314and a second stop voltage controller 315. The first stop voltagecontroller 314 and the second stop voltage controller 315 may provide afirst stop voltage and a second stop voltage based on the first stopvoltage control signal L_CS_SVC1 and the second stop voltage controlsignal L_CS_SVC2.

For example, during the clock stop time interval CSTI, the first stopvoltage controller enable signal EN_SVC1 and the second stop voltagecontroller enable signal EN_SVC2 may be enabled, in which case, thefirst stop voltage controller 314 and the second stop voltage controller315 may be turned-on. In the event the first stop voltage controller 314and the second stop voltage controller 315 are turned-on during theclock stop time interval CSTI, the first stop voltage and the secondstop voltage may be decreased based on the first stop voltage controlsignal L_CS_SVC1 and the second stop voltage control signal L_CS_SVC2.

In an exemplary embodiment, the stop voltage controllers 314 and 315 mayinclude a first stop voltage controller 314 and a second stop voltagecontroller 315. A level of a first stop voltage that is provided fromthe first stop voltage controller 314 may be different from a level of asecond stop voltage that is provided from the second stop voltagecontroller 315. For example, the first stop voltage may be 0.7V and thesecond stop voltage may be 0.9V

FIG. 10 is a diagram for describing operation of stop voltagecontrollers included in the internal voltage control unit of FIG. 4.

Referring to FIG. 10, during the clock stop time interval CSTI, thepower supply voltage may be required in a part of the sub-units 300. Forexample, during the clock stop time interval CSTI, the power supplyvoltage may be required in a logic circuit unit 318 and SRAM 319 of thesub-units 300. During the clock stop time interval CSTI, the first stopvoltage STOP IVC1 that is provided from the first stop voltagecontroller 314 may be provided to a logic circuit unit 318 included inthe smart card 10. The second stop voltage STOP IVC2 that is providedfrom the second stop voltage controller 315 may be provided to SRAM 319included in the smart card 10.

In this case, during the clock stop time interval CSTI, a voltage levelof the power supply voltage that is provided to the part of thesub-units 300 during the clock stop time interval CSTI may be less thanthe voltage level of the power supply voltage that is provided to thesub-units 300 during an active time interval when the data istransferred between the smart card 10 and the card reader. For example,the voltage level that is provided to the logic circuit unit 318 andSRAM 319 during an active time interval when the data is transferredbetween the smart card 10 and the card reader may be 1.1V. The voltagelevel that is provided to the logic circuit unit 318 of the sub-units300 during the clock stop time interval CSTI may be 0.7V. The voltagelevel that is provided to SRAM 319 of the sub-units 300 during the clockstop time interval CSTI may be 0.8V. In this manner, during the clockstop time interval CSTI, the voltage level of the power supply voltagethat is provided to the logic circuit unit 318 and SRAM 319 of thesub-units 300 may be decreased. For example, the voltages that areprovided to the sub-units 300 may include the first stop voltage STOPIVC1 and the second stop voltage STOP IVC2.

In an exemplary embodiment, during the clock stop time interval CSTI,the first stop voltage STOP IVC1 that is provided from the first stopvoltage controller 314 may be provided to a logic circuit unit 318included in the smart card 10. The second stop voltage STOP IVC2 that isprovided from the second stop voltage controller 315 may be provided toSRAM 319 included in the smart card 10.

A method of operating a smart card 10 according to exemplary embodimentsmay decrease the power consumption by controlling the voltages that areprovided to the sub-units 300 based on the control signal CS_SVC and thelevel control signals L_CS_SVC during the clock stop time interval CSTI.

FIG. 11 is a timing diagram for describing operation of an oscillatorunit 330 included in the smart card of FIG. 3 during a clock stop timeinterval.

Referring to FIG. 11, the clock stop time interval CSTI may be a timeinterval when the first stop signal SS1 is the second logic level andthe second stop signal SS2 is the second logic level.

In an exemplary embodiment, during the clock stop time interval CSTI,the plurality of oscillators 331 to 333 may be turned-off. Theoscillator enable signal EN_OS may include first to third oscillatorsignals OSC1, OSC2 and OSC3. During the clock stop time interval CSTI,the first to third oscillator signals OSC1, OSC2 and OSC3 may bedisabled and, as a result, the first to third oscillators 331 to 333 maybe turned-off.

In an exemplary embodiment, during the clock stop time interval CSTI,the stop voltage controllers 314 and 315 may be turned-on and the activevoltage controllers 311 to 313 may be turned-off. For example, theinternal voltage control unit 310 may include a plurality of activevoltage controllers 311 to 313 and a plurality of stop voltagecontrollers 314 and 315. The active voltage controllers 311 to 313 mayinclude a first active voltage controller 311, a second active voltagecontroller 312 and a third active voltage controller 313. The stopvoltage controllers 314 and 315 may include a first stop voltagecontroller 314 and a second stop voltage controller 315. The voltagecontroller enable signal may include the first to third active voltagecontroller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 and the first tosecond stop voltage controller enable signals EN_SVC1 and EN_SVC2.During the clock stop time interval CSTI, the first to third activevoltage controller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 may bedisabled and the first to second stop voltage controller enable signalsEN_SVC1 and EN_SVC2 may be enabled. In the event, during the clock stoptime interval CSTI, the first to third active voltage controller enablesignals EN_AVC1, EN_AVC2 and EN_AVC3 are disabled and the first tosecond stop voltage controller enable signals EN_SVC1 and EN_SVC2 areenabled, the first to third active voltage controllers 311 to 313 may beturned-off and the first to second stop voltage controllers 314 and 315may be turned-on.

FIG. 12 is a state diagram for describing states of an oscillator unitand an internal voltage control unit included in the smart card of FIG.3 during a clock stop time interval.

Referring to FIGS. 4, 5 and 12, the plurality of sub-units 300 mayinclude an internal voltage control unit 310 and an oscillator unit 330.The internal voltage control unit 310 may include a plurality of activevoltage controllers 311 to 313 and a plurality of stop voltagecontrollers 314 and 315. The oscillator unit 330 may include a pluralityof oscillators 331 to 333. The clock stop time interval CSTI may be atime interval when the first stop signal SS1 is the second logic leveland the second stop signal SS2 is the second logic level.

During the clock stop time interval CSTI, the active voltage controllers311 to 313 included in the internal voltage control unit 310 may beturned-off. During the clock stop time interval CSTI, the oscillators331 to 333 included in the oscillator unit 330 may be turned-off. Duringthe clock stop time interval CSTI, the stop voltage controllers 314 and315 included in the internal voltage control unit 310 may be turned-on.

FIG. 13 is a timing diagram for describing operation of an oscillatorunit included in the smart card of FIG. 3 during a second idle timeinterval.

Referring to FIGS. 5 and 13, the second idle time interval ITI2 may be atime interval when the first stop signal SS1 is the second logic leveland the second stop signal SS2 is the first logic level after the clockstop time interval CSTI.

In an exemplary embodiment, the external clock signal ECLK may beactivated during the second idle time interval ITI2. For example, thefrequency detector 400 may detect the external clock signal ECLK. In theevent the external clock signal ECLK is deactivated, the frequencydetector 400 may control the second stop signal SS2 so that the secondstop signal SS2 transitions from the first logic level to the secondlogic level. During the first idle time interval ITI1, the externalclock signal ECLK may be activated. During the clock stop time intervalCSTI, the external clock signal ECLK may be deactivated. During thesecond idle time interval ITI2, the external clock signal ECLK may beactivated.

In an exemplary embodiment, during the second idle time interval ITI2,the plurality of oscillators 331 to 333 may be sequentially turned-onbased on oscillator enable signals EN_OS1, EN_OS2 and EN_OS3 of theplurality of enable signals EN_VC, EN_OS. For example, the oscillators331 to 333 may include a first oscillator 331, a second oscillator 332and a third oscillator 333. The oscillator enable signals EN_OS1, EN_OS2and EN_OS3 of the enable signals EN_VC, EN_OS may include first to thirdoscillator enable signals EN_OS1, EN_OS2 and EN_OS3. During the secondidle time interval ITI2, the first to third oscillator enable signalsEN_OS1, EN_OS2 and EN_OS3 may be sequentially enabled and, as a result,the second oscillator 332 may be turned-on after the first oscillator331 is turned-on and the third oscillator 333 may be turned-on after thesecond oscillator 332 is turned-on.

FIG. 14 is a timing diagram for describing operation of an internalvoltage control unit included in the smart card of FIG. 3 during asecond idle time interval.

Referring to FIGS. 4 and 14, the internal voltage control unit 310 mayinclude a plurality of active voltage controllers 311 to 313 and aplurality of stop voltage controllers 314 and 315. The active voltagecontrollers 311 to 313 may include a first active voltage controller311, a second active voltage controller 312 and a third active voltagecontroller 313. The stop voltage controllers 314 and 315 may include afirst stop voltage controller 314 and a second stop voltage controller315. For example, the first to third active voltage controllers 311 to313 may provide a first to third active voltages based on the first tothird active voltage controller enable signals EN_AVC1, EN_AVC2 andEN_AVC3. The first to second stop voltage controllers 314 and 315 mayprovide a first to second stop voltages based on the first to secondstop voltage controller enable signals EN_SVC1 and EN_SVC2.

In an exemplary embodiment, during the second idle time interval ITI2,the stop voltage controllers 314 and 315 may be turned-on based on stopvoltage controller enable signals EN_SVC1 and EN_SVC2. For example,during the second idle time interval ITI2, the first to second stopvoltage controller enable signals EN_SVC1 and EN_SVC2 may be enabledand, as a result, the first to second stop voltage controllers 314 and315 may be turned-on. In this case, the voltage level that is providedto the stop voltage controllers 314 and 315 may be controlled based onthe stop voltage control signal. For example, during the second idletime interval ITI2, the voltage level that is provided to the stopvoltage controllers 314 and 315 may be 1.1V.

During the second idle time interval ITI2, the plurality of activevoltage controllers 311 to 313 may be sequentially turned-on based onactive voltage controller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 ofthe plurality of enable signals EN_VC, EN_OS. For example, the first tothird active voltage controller enable signals EN_AVC1, EN_AVC2 andEN_AVC3 may be sequentially enabled. During the second idle timeinterval ITI2, the second active voltage controller enable signalEN_AVC2 may be enabled after the first active voltage controller enablesignal EN_AVC1 is enabled and the third active voltage controller enablesignal EN_AVC3 may be enabled after the second active voltage controllerenable signal EN_AVC2 is enabled. In this case, the second activevoltage controller 312 may be turned-on after the first active voltagecontroller 311 is turned-on and the third active voltage controller 313may be turned-on after the second active voltage controller 312 isturned-on.

FIG. 15 is a state diagram for describing states of an oscillator unitand an internal voltage control unit included in the smart card of FIG.3 during a second idle time interval.

Referring to FIGS. 4, 5 and 15, the plurality of sub-units 300 mayinclude an internal voltage control unit 310 and an oscillator unit 330.The internal voltage control unit 310 may include a plurality of activevoltage controllers 311 to 313 and a plurality of stop voltagecontrollers 314 and 315. The oscillator unit 330 may include a pluralityof oscillators 331 to 333. The second idle time interval ITI2 may be atime interval when the first stop signal SS1 is the second logic leveland the second stop signal SS2 is the first logic level after the clockstop time interval CSTI.

During the second idle time interval ITI2, the active voltagecontrollers 311 to 313 included in the internal voltage control unit 310may be sequentially turned-on. During the second idle time intervalITI2, the oscillators 331 to 333 included in the oscillator unit 330 maybe sequentially turned-on. During the first idle time interval ITI1, thestop voltage controllers 314 and 315 included in the internal voltagecontrol unit 310 may be turned-on.

FIG. 16 is a timing diagram for describing operation of an oscillatorunit and an internal voltage control unit included in the smart card ofFIG. 3 during a first idle time interval, a clock stop time intervalCSTI and a second idle time interval. FIG. 17 is a diagram illustratinga current specification according to ETSI TS 102 221 that is aspecification of a smart card.

Referring to FIGS. 16 and 17, the plurality of sub-units 300 may includean internal voltage control unit 310 and an oscillator unit 330. Theinternal voltage control unit 310 may include a plurality of activevoltage controllers 311 to 313 and a plurality of stop voltagecontrollers 314 and 315. The oscillator unit 330 may include a pluralityof oscillators 331 to 333. the first idle time interval ITI1 may be atime interval when the first stop signal SS1 is the second logic leveland the second stop signal SS2 is the first logic level after the datatransmission is completed. The clock stop time interval CSTI may be atime interval when the first stop signal SS1 is the second logic leveland the second stop signal SS2 is the second logic level. The secondidle time interval ITI2 may be a time interval when the first stopsignal SS1 is the second logic level and the second stop signal SS2 isthe first logic level after the clock stop time interval CSTI.

During the first idle time interval ITI1, the plurality of activevoltage controllers 311 to 313 may be sequentially turned-off based onactive voltage controller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 ofthe plurality of enable signals EN_VC, EN_OS. During the first idle timeinterval ITI1, the plurality of oscillators 331 to 333 may besequentially turned-off based on oscillator enable signals EN_OS1,EN_OS2 and EN_OS3 of the plurality of enable signals EN_VC, EN_OS.During the first idle time interval ITI1, the plurality of stop voltagecontrollers 314 and 315 may be turned-on based on stop voltagecontroller enable signals EN_SVC1 and EN_SVC2 of the plurality of enablesignals EN_VC, EN_OS.

During the clock stop time interval CSTI, the plurality of activevoltage controllers 311 to 313 may be turned-off. During the clock stoptime interval CSTI, the plurality of oscillators 331 to 333 may beturned-off. During the clock stop time interval CSTI, the plurality ofstop voltage controllers 314 and 315 may be turned-on.

During the second idle time interval ITI2, the plurality of activevoltage controllers 311 to 313 may be sequentially turned-on based onactive voltage controller enable signals EN_AVC1, EN_AVC2 and EN_AVC3 ofthe plurality of enable signals EN_VC, EN_OS. During the first idle timeinterval ITI1, the plurality of oscillators 331 to 333 may besequentially turned-on based on oscillator enable signals EN_OS1, EN_OS2and EN_OS3 of the plurality of enable signals EN_VC, EN_OS. During thefirst idle time interval ITI1, the plurality of stop voltage controllers314 and 315 may be turned-on based on stop voltage controller enablesignals EN_SVC1 and EN_SVC2 of the plurality of enable signals EN_VC,EN_OS.

In class B and the class C, the current according to EuropeanTelecommunications Standards Institute Technical Specification (ETSI TS)102 221, which is a specification of the smart card 10, may be less than200 uA during the idle time interval. In class B and the class C, thecurrent according to ETSI TS 102 221 may be less than 100 uA during theclock stop time interval CSTI. The current according to ETSI TS 102 221during the idle time interval may be less than the current according toETSI TS 102 221 during the clock stop time interval CSTI. The method ofoperating a smart card 10 according to exemplary embodiments maydecrease the power consumption by controlling the voltages that areprovided to the sub-units 300 based on the control signal CS_SVC and thelevel control signals L_CS_SVC during the clock stop time interval CSTI.

FIG. 18 is a block diagram illustrating a smart card according to anexemplary embodiment and FIG. 19 is a block diagram illustrating anexample of a detector unit included in the smart card of FIG. 18.

Referring to FIGS. 18 and 19, a smart card 10 a may include a CPU 100, apower management unit 200, a plurality of sub-units 300, a frequencydetector 400 and a detector unit 350. The smart card 10 may receive apower supply voltage VDD, an external clock signal ECLK and input-outputsignal SIO. When data transmission is completed between the smart card10 and a card reader, the CPU 100 may provide a power stop command C_POto the power management unit 200. The power management unit 200 mayactivate or deactivate the sub-units 300 based on the enable signalsEN_VC, EN_OS.

In the event the power management unit 200 deactivates the sub-units 300based on the enable signals EN_VC, EN_OS, the power supply voltage thatis provided to the sub-units 300 may be blocked (also referred to hereinas, “turned off,” or “cut off,” or “disabled”). In the event the powermanagement unit 200 activates the sub-units 300 based on the enablesignals EN_VC, EN_OS, the power supply voltage may be provided to thesub-units 300.

The frequency detector 400 may detect whether the frequency of theexternal clock signal ECLK is within a predetermined range or not.During the clock stop time interval CSTI, the frequency detector 400 maystop detecting whether the frequency of the external clock signal ECLKis within the predetermined range and may detect only whether theexternal clock signal ECLK is activated or not. During the clock stoptime interval CSTI, the power management unit 200 and a frequencydetector 400 control voltages provided to sub-units 300, based on acontrol signal CS_SVC and level control signals L_CS_SVC. The controlsignal CS_SVC is generated from the frequency detector 400 by detectingthe external clock signal ECLK. The level control signals L_CS_SVC aregenerated from the power management unit 200 based on the control signalCS_SVC. In the event the external clock signal ECLK is disabled, thefrequency detector 400 may provide the control signal CS_SVC to theinternal voltage control unit 310 and the power management unit 200 bydetecting the deactivation of the external clock signal ECLK. The powermanagement unit 200 may generate the level control signals L_CS_SVCbased on the control signal CS_SVC. The power management unit 200 maycontrol the voltages that are provided to the sub-units 300, based onthe level control signals L_CS_SVC. A time interval when the externalclock signal ECLK is deactivated may be the clock stop time intervalCSTI. The level of the voltages that are provided to the sub-units 300may be controlled based on the control signal CS_SVC and the levelcontrol signals L_CS_SVC. In the event the level of the voltages thatare provided to the sub-units 300 is controlled, the level of the outputvoltages that are outputted from the sub-units 300 may be controlled.

In an exemplary embodiment, the plurality of sub-units 300 may furtherinclude a detector unit 350. The detector unit 350 may include aplurality of detectors that detect an internal environment of the smartcard 10. The plurality of detectors may be activated and deactivatedbased on the plurality of enable signals EN_VC, EN_OS. For example, thedetectors may include a first detector 351 and a second detector 352.The first detector 351 may detect temperature in the smart card 10. Thesecond detector 352 may detect a voltage level of the sub-units 300. Thefirst detector 351 may be turned-on or turned-off based on a firstdetector enable signal EN_DE1. The second detector 352 may be turned-onor turned-off based on a second detector enable signal EN_DE2. The firstdetector 351 may provide a detection result of the temperature as afirst detector result signal DEL The second detector 352 may provide adetection result of the voltage level as a second detector result signalDE2.

FIG. 20 is a timing diagram for describing operation of a detector unitincluded in the smart card of FIG. 18 during a first idle time interval,a clock stop time interval and a second idle time interval.

Referring to FIG. 20, during the first idle time interval ITI1, theplurality of detectors may be sequentially turned-off based on detectorenable signals of the plurality of enable signals EN_VC, EN_OS. Duringthe clock stop time interval CSTI, the plurality of detectors may beturned-off During the second idle time interval ITI2, the plurality ofdetectors may be sequentially turned-on based on the detector enablesignals EN_VC, EN_OS. For example, during the first idle time intervalITI1, the second detector enable signal EN_DE2 may be disabled after thefirst detector enable signal EN_DE1 is disabled. In this case, thesecond detector 352 may be turned-off after the first detector 351 isturned-off. During the clock stop time interval CSTI, the first detectorenable signal EN_DE1 and the second detector enable signal EN_DE2 may bedisabled. In this case, the first detector 351 and the second detectormay be turned-off. During the second idle time interval ITI2, the seconddetector enable signal EN_DE2 may be enabled after the first detectorenable signal EN_DE1 is enabled. In this case, the second detector maybe turned-on after the first detector 351 is turned-on.

FIG. 21 is a block diagram illustrating a smart card according toexemplary embodiments and FIG. 22 is a diagram for describing operationof a reset unit included in the smart card of FIG. 21.

Referring to FIGS. 21 and 22, smart card 10 b may include a CPU 100, apower management unit 200, a plurality of sub-units 300, a frequencydetector 400, a reset unit 370 and a pad unit 390. The smart card 10 bmay receive a power supply voltage VDD, an external clock signal ECLKand input-output signal SIO. When data transmission is completed betweenthe smart card 10 b and a card reader, the CPU 100 may provide a powerstop command C_PO to the power management unit 200. The power managementunit 200 may activate or deactivate the sub-units 300 based on theenable signals EN_VC, EN_OS. The frequency detector 400 may detectwhether the frequency of the external clock signal ECLK is within apredetermined range or not. During the clock stop time interval CSTI,the frequency detector 400 may stop detecting whether the frequency ofthe external clock signal ECLK is within the predetermined range and maydetect only whether the external clock signal ECLK is activated or not.During the clock stop time interval CSTI, the power management unit 200and a frequency detector 400 control voltages provided to sub-units 300,based on a control signal CS_SVC and level control signals L_CS_SVC. Thecontrol signal CS_SVC is generated from the frequency detector 400 bydetecting the external clock signal ECLK. The level control signalsL_CS_SVC are generated from the power management unit 200 based on thecontrol signal CS_SVC.

In an exemplary embodiment, the plurality of sub-units 300 may furtherinclude a reset unit 370. The reset unit 370 may reset the smart card 10b in the event internal voltage of the smart card 10 b is less than apredetermined voltage. During the clock stop time interval CSTI, thereset unit 370 may be turned-off based on a reset enable signal EN_RE ofthe plurality of enable signals EN_VC, EN_OS and EN_RE. For example, inthe event the voltage that is provided from the internal voltage controlunit 310 is less than 0.99V, the reset unit 370 may reset the smart card10 b. During the clock stop time interval CSTI, the voltage that isprovided from the internal voltage control unit 310 may be less than0.99V. If the reset unit 370 is turned-off during the clock stop timeinterval CSTI, the smart card 10 b may not be reset even though thevoltage that is provided from the internal voltage control unit 310 isless than 0.99V. Therefore, during the clock stop time interval CSTI,the reset unit 370 may be turned-off based on a reset enable signalEN_RE.

In an exemplary embodiment, the plurality of sub-units 300 may furtherinclude a pad unit 390 that receives external signals. During the clockstop time interval CSTI, the pad unit 390 may be turned-on andturned-off based on a pad enable signal EN_PD of the plurality of enablesignals. For example, during the clock stop time interval CSTI, thepower supply voltage may be provided to a clock pad. In this case, theclock pad included in the pad unit 390 may be turned-on. For example,during the clock stop time interval CSTI, data may not be transferredthrough an input-output pad. Therefore the power supply voltage may beblocked in the input-output pad. In this case, the input-output padincluded in the pad unit 390 may be turned-off.

FIG. 23 is a flow chart illustrating a method of operating a smart cardsystem according to exemplary embodiments and FIG. 24 is a block diagramillustrating a smart card system according to exemplary embodiments.

Referring to FIGS. 23 and 24, a smart card system 20 may include a cardreader 15 and a smart card 10. The card reader 15 may provide a powersupply voltage VDD, an external clock signal ECLK and an input-outputsignal SIO. The smart card 10 may include a CPU 100, a power managementunit 200, a plurality of sub-units 300 and a frequency detector 400. Thesmart card 10 may receive a power supply voltage VDD, an external clocksignal ECLK and input-output signal SIO. When data transmission iscompleted between the smart card 10 and a card reader, the CPU 100 mayprovide a power stop command C_PO to the power management unit 200. Thepower management unit 200 may activate or deactivate the sub-units 300based on the enable signals EN_VC, EN_OS.

The frequency detector 400 may detect whether the frequency of theexternal clock signal ECLK is within a predetermined range or not.During the clock stop time interval CSTI, the frequency detector 400 maystop detecting whether the frequency of the external clock signal ECLKis in the predetermined range and may detect only whether the externalclock signal ECLK is activated or not. During the clock stop timeinterval CSTI, the power management unit 200 and a frequency detector400 control voltages provided to sub-units 300, based on a controlsignal CS_SVC and level control signals L_CS_SVC. The control signalCS_SVC is generated from the frequency detector 400 by detecting theexternal clock signal ECLK. The level control signals L_CS_SVC aregenerated from the power management unit 200 based on the control signalCS_SVC. In the event the external clock signal ECLK is disabled, thefrequency detector 400 may provide the control signal CS_SVC to theinternal voltage control unit 310 and the power management unit 200 bydetecting the deactivation of the external clock signal ECLK. The powermanagement unit 200 may generate the level control signals L_CS_SVCbased on the control signal CS_SVC. The power management unit 200 maycontrol the voltages that are provided to the sub-units 300, based onthe level control signals L_CS_SVC. A time interval when the externalclock signal ECLK is deactivated may be the clock stop time intervalCSTI. The level of the voltages that are provided to the sub-units 300may be controlled based on the control signal CS_SVC and the levelcontrol signals L_CS_SVC. In the event the level of the voltages thatare provided to the sub-units 300 is controlled, the level of the outputvoltages that are outputted from the sub-units 300 may be controlled.

In a method of operating a smart card 10 according to exemplaryembodiments, data is transferred between the card reader and the smartcard 10 (S200). The power management unit 200 deactivates a plurality ofsub-units 300 based on a plurality of enable signals EN_VC, EN_(—) OSduring a first idle time interval ITI1 (S210). A first stop signal SS1is a second logic level and a second stop signal SS2 is a first logiclevel based on a external clock signal ECLK during the first idle timeinterval ITI1 after data transmission is completed.

The power management unit 200 and a frequency detector 400 controlvoltages provided to sub-units 300, based on a control signal CS_SVC andlevel control signals L_CS_SVC during a clock stop time interval CSTI(S220). The control signal CS_SVC is generated from the frequencydetector 400. The level control signals L_CS_SVC are generated from thepower management unit 200 based on the control signal CS_SVC. The firststop signal SS1 is the second logic level and the second stop signal SS2is the second logic level based on the external clock signal ECLK duringthe clock stop time interval CSTI after the first idle time intervalITI1. The power management unit 200 activates the plurality of sub-units300 based on the plurality of enable signals EN_VC, EN_OS during asecond idle time interval ITI2 (S230). The first stop signal SS1 is thesecond logic level and the second stop signal SS2 is the first logiclevel based on the external clock signal ECLK during the second idletime interval ITI2 after the clock stop time interval CSTI. The methodof operating a smart card 10 according to exemplary embodiments maydecrease the power consumption by controlling the voltages that areprovided to the sub-units 300 based on the control signal CS_SVC and thelevel control signals L_CS_SVC during the clock stop time interval CSTI.

FIG. 25 is a flow chart illustrating a method of operating a smart cardaccording to exemplary embodiments and FIG. 26 is a timing diagram fordescribing the method of operating the smart card of FIG. 25.

Referring to FIGS. 25 and 26, in a method of operating a smart card 10,a power management unit 200 deactivates a plurality of sub-units 300based on a plurality of enable signals EN_VC, EN_OS during a first stoptime interval STI1 (S300). A first stop signal SS1 is a second logiclevel and a second stop signal SS2 is a first logic level based on thefirst stop signal SS1 during the first stop time interval STI1 afterdata transmission is completed. The second stop signal SS2 may begenerated from the detector based on the first stop signal SS1. Forexample, in the event the external clock signal ECLK is not provided tothe smart card 10, the method of operating the smart card 10 that isdescribed in FIGS. 25 and 26 may be applied.

The power management unit 200 and a detector control voltages providedto sub-units 300, based on a control signal CS_SVC and level controlsignals L_CS_SVC during a second stop time interval STI2 after the firststop time interval STI1 (S310). The control signal CS_SVC is generatedfrom the detector. The level control signals L_CS_SVC are generated fromthe power management unit 200 based on the control signal CS_SVC. Thepower management unit 200 activates the plurality of sub-units 300 basedon the plurality of enable signals EN_VC, EN_OS during a third stop timeinterval STI3 (S320). In exemplary embodiments the third stop timeinterval STI3 is before the first stop signal SS1 transitions from thesecond logic level to the first logic level after the second stop timeinterval STI2. The method of operating a smart card 10 according toexemplary embodiments may decrease the power consumption by controllingthe voltages that are provided to the sub-units 300 based on the controlsignal CS_SVC and the level control signals L_CS_SVC during the secondstop time interval STI2.

FIG. 27 is a block diagram illustrating a mobile system according to anexemplary embodiment.

Referring to FIG. 16, a mobile system 1000 includes an applicationprocessor 1100, a contactless smart card such as an IC card 1200, amemory 1310, a user interface 1320, a connectivity unit 1330, and apower supply 1340. According to at least one exemplary embodiment, themobile system 1000 may be any mobile system, such as a mobile phone, asmart phone, a personal digital assistant (PDA), a portable multimediaplayer (PMP), a digital camera, a portable game console, a music player,a camcorder, a video player, a navigation system, etc.

The application processor 1100 may execute applications, such as a webbrowser, a game application, a video player, etc. In at least oneexemplary embodiment, the application processor 1100 may include asingle core or multiple cores. For example, the application processor1100 may be a multi-core processor, such as a dual-core processor, aquad-core processor, a hexa-core processor, etc. According to at leastone example, the application processor 1110 may be coupled to aninternal/external cache memory.

The memory device 1310 may store a boot image for booting the mobilesystem 1000, output data to be transmitted to an external device, andinput data from the external device. For example, the memory device 1310may be an electrically erasable programmable read-only memory (EEPROM),a flash memory, a phase change random access memory (PRAM), a resistancerandom access memory (RRAM), a nano floating gate memory (NFGM), apolymer random access memory (PoRAM), a magnetic random access memory(MRAM), a ferroelectric random access memory (FRAM), etc.

The contactless smart card 1200 selects the reference voltage for theregulator in the internal voltage generator according to operation modethat is determined based on whether the internal circuit performs anencryption operation. Thus, a fluctuation component is inhibited (oralternatively, prevented) from being transferred to the input voltage.Therefore, the contactless smart card 1200 may reduce (or alternatively)prevent transmission errors that may occur when the internal circuitperforms encryption operation.

The user interface 1320 may include at least one input device, such as akeypad, a touch screen, etc., and at least one output device, such as aspeaker, a display device, etc. The power supply 1340 may supply a powersupply voltage to the mobile system 1000.

The connectivity unit 1330 may perform wired or wireless communicationwith an external device. For example, the connectivity unit 1330 mayperform Ethernet communication, near field communication (NFC), radiofrequency identification (RFID) communication, mobile telecommunication,memory card communication, universal serial bus (USB) communication,etc. In at least one exemplary embodiment, connectivity unit 1330 mayinclude a baseband chipset that supports communications, such as globalsystem for mobile communications (GSM), general packet radio service(GPRS), wideband code division multiple access (WCDMA), high speeddownlink/uplink packet access (HSxPA), etc.

In at least one exemplary embodiment, the mobile system 1000 may furtherinclude a camera image processor (CIS), and/or a storage device, such asa memory card, a solid state drive (SSD), a hard disk drive (HDD), aCD-ROM, etc.

In at least one exemplary embodiment, the mobile system 1000 and/orcomponents of the mobile system 1000 may be packaged in various forms,such as package on package (PoP), ball grid arrays (BGAs), chip scalepackages (CSPs), plastic leaded chip carrier (PLCC), plastic dualin-line package (PDIP), die in waffle pack, die in wafer form, chip onboard (COB), ceramic dual in-line package (CERDIP), plastic metric quadflat pack (MQFP), thin quad flat pack (TQFP), small outline IC (SOIC),shrink small outline package (SSOP), thin small outline package (TSOP),system in package (SIP), multi-chip package (MCP), wafer-levelfabricated package (WFP), or wafer-level processed stack package (WSP).

Various exemplary embodiments may be widely applicable to variouscontactless smart cards, such as IC cards, and card systems. If thereader receiver according to exemplary embodiments is implemented, thedesign size and the power consumption of the communication systemincluding the reader receiver may be decreased.

The foregoing is illustrative of exemplary embodiments and is not to beconstrued as limiting thereof. Although a few exemplary embodiments havebeen described, those skilled in the art will readily appreciate thatmany modifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings and advantages ofinventive concepts. Accordingly, all such modifications are intended tobe included within the scope of inventive concepts as defined in theclaims. Therefore, it is to be understood that the foregoing isillustrative of various exemplary embodiments and is not to be construedas limited to the specific exemplary embodiments disclosed, and thatmodifications to the disclosed exemplary embodiments, as well as otherexemplary embodiments, are intended to be included within the scope ofthe appended claims.

What is claimed is:
 1. A method of operating a smart card comprising:deactivating, by a power management unit, a plurality of sub-units basedon a plurality of enable signals during a first idle time interval, afirst stop signal set to a second logic level and a second stop signalset to a first logic level during the first idle time interval afterdata transmission is completed, the second stop signal being generatedfrom a frequency detector based on a external clock signal; controlling,by the power management unit and a frequency detector, voltages based ona control signal and level control signals during a clock stop timeinterval, the voltages being provided to the sub-units, the controlsignal being generated from the frequency detector, the level controlsignals being generated from the power management unit based on thecontrol signal, the first stop signal set to the second logic level andthe second stop signal set to the second logic level based on theexternal clock signal during the clock stop time interval after thefirst idle time interval; and activating, by the power management unit,the plurality of sub-units based on the plurality of enable signalsduring a second idle time interval, the first stop signal set to thesecond logic level and the second stop signal set to the first logiclevel based on the external clock signal during the second idle timeinterval after the clock stop time interval.
 2. The method of claim 1,wherein the plurality of sub-units includes an internal voltage controlunit and an oscillator unit, wherein the internal voltage control unitincludes a plurality of active voltage controllers and a plurality ofstop voltage controllers, wherein the oscillator unit includes aplurality of oscillators, and wherein the plurality of active voltagecontrollers, the plurality of stop voltage controllers and the pluralityof oscillators are activated and deactivated based on the plurality ofenable signals.
 3. The method of claim 2, wherein the external clocksignal is activated during the first idle time interval, and wherein,during the first idle time interval, the plurality of oscillators aresequentially turned-off based on oscillator enable signals of theplurality of enable signals.
 4. The method of claim 3, wherein, duringthe first idle time interval, the plurality of stop voltage controllersare turned-on based on stop voltage controller enable signals of theplurality of enable signals, and wherein the plurality of active voltagecontrollers are sequentially turned-off based on active voltagecontroller enable signals of the plurality of enable signals.
 5. Themethod of claim 2, wherein the external clock signal is deactivatedduring the clock stop time interval, wherein, during the clock stop timeinterval, the frequency detector stops detecting whether a frequency ofthe external clock signal is within a predetermined range and detectswhether the external clock signal is activated or not, and wherein thefrequency detector and the power management unit control the voltagesbased on stop voltage control signals of the level control signals andthe control signal during the clock stop time interval, the voltagesbeing provided to the stop voltage controllers, the level controlsignals being generated from the power management unit based on thecontrol signal.
 6. The method of claim 5, wherein the stop voltagecontrollers includes a first stop voltage controller and a second stopvoltage controller, wherein a level of a first stop voltage that isprovided from the first stop voltage controller is different from alevel of a second stop voltage that is provided from the second stopvoltage controller.
 7. The method of claim 6, wherein the first stopvoltage that is provided from the first stop voltage controller isprovided to a logic circuit unit included in the smart card, and whereinthe second stop voltage that is provided from the second stop voltagecontroller is provided to SRAM included in the smart card.
 8. The methodof claim 7, wherein, during the clock stop time interval, the pluralityof oscillators are turned-off, and wherein, during the clock stop timeinterval, the stop voltage controllers are turned-on and the activevoltage controllers are turned-off.
 9. The method of claim 2, whereinthe external clock signal is activated during the second idle timeinterval, and wherein, during the second idle time interval, theplurality of oscillators are sequentially turned-on based on oscillatorenable signals of the plurality of enable signals.
 10. The method ofclaim 9, wherein, during the second idle time interval, the stop voltagecontrollers are turned-on based on stop voltage controller enablesignals, and wherein, during the second idle time interval, theplurality of active voltage controllers are sequentially turned-on basedon active voltage controller enable signals of the plurality of enablesignals.
 11. The method of claim 2, wherein the plurality of sub-unitsfurther includes a detector unit, wherein the detector unit includes aplurality of detectors that detect internal environment of the smartcard, and wherein the plurality of detectors are activated anddeactivated based on the plurality of enable signals.
 12. The method ofclaim 11, wherein, during the first idle time interval, the plurality ofdetectors are sequentially turned-off based on detector enable signalsof the plurality of enable signals, wherein, during the clock stop timeinterval, the plurality of detectors are turned-off, and wherein, duringthe second idle time interval, the plurality of detectors aresequentially turned-on based on the detector enable signals.
 13. Themethod of claim 2, wherein, the plurality of sub-units further includesa reset unit, the reset unit resetting the smart card in the eventinternal voltage of the smart card is less than a predetermined voltage,and wherein, during the clock stop time interval, the reset unit isturned-off based on a reset enable signal of the plurality of enablesignals.
 14. The method of claim 2, wherein the plurality of sub-unitsfurther includes a pad unit that receives external signals, and wherein,during the clock stop time interval, the pad unit is turned-on or -offbased on a pad enable signal of the plurality of enable signals.
 15. Amethod of operating a smart card comprising: deactivating, by a powermanagement unit, a plurality of sub-units based on a plurality of enablesignals during a first stop time interval, a first stop signal set to asecond logic level and a second stop signal set to a first logic levelduring the first stop time interval after data transmission iscompleted, the second stop signal being generated from a detector basedon the first stop signal; controlling, by the power management unit andthe detector, voltages based on a control signal and level controlsignals during a second stop time interval after the first stop timeinterval, the voltages being provided to the sub-units, the controlsignal being generated from the detector, the level control signalsbeing generated from the power management unit based on the controlsignal; and activating, by the power management unit, the plurality ofsub-units based on the plurality of enable signals during a third stoptime interval, the third stop time interval being before the first stopsignal transitions from the second logic level to the first logic levelafter the second stop time interval.
 16. A smart card, comprising: datastorage and transmission circuitry; a plurality of voltage controllersto supply operational power to card circuitry; a plurality ofoscillators to supply an internal clock for the card; and powermanagement circuitry to shut down the oscillators and at least one, butnot all, voltage controllers during a period after a data transmissionis completed.
 17. The smart card of claim 16, wherein the powermanagement circuitry is further configured to reduce the voltage outputof a voltage controller that has not been shut down when an externalclock is deactivated.
 18. The smart card of claim 17, wherein the powermanagement circuitry is further configured to turn on the oscillatorsand voltage controllers that had been shut down and to return the outputvoltage of a voltage controller whose output voltage had been reducedwhen the external clock is activated.
 19. The smart card of claim 16,wherein the power management circuitry shuts down the oscillators insequence.
 20. The smart card of claim 16, wherein the power managementcircuitry shuts down a plurality of voltage controllers in sequence.